This invention relates to salts of acid ether sulphates which are in the liquid state under normal temperature and pressure conditions and to a method for preparing these salts.
Salts having very good surface activity can be prepared by neutralization of acid sulphates of the general formula R(OCH.sub.2 CH.sub.2).sub.n OSO.sub.2 OH, where n represents a number having an average value of 2 to 3 and R is an alkyl group with 8 to 16 carbon atoms with an amine from the group of diethylamine, butylethanolamine, and isopropylamine or mixtures thereof as disclosed in British Pat. No. 891,631.
Also known are sodium salts of acid sulfates corresponding to the formula C.sub.12 H.sub.25 (OCH.sub.2 CH.sub.2).sub.n OSO.sub.2 OH. Neutralization of the acid sulfate with sodium hydroxide yields a neutral salt having a very good surface-active activity. As the n value in this formula increases the consistency undergoes a gradual change from a solid through a paste like state to a liquid state. For instance with sodium lauryl sulfate where n=o the salt is a solid. Surface activity does not increase substantially for n&gt;3 and for higher n values the cost of the product increases. Therefore in practice n values are about 3 or less. With an n value in excess of 3 these sodium salts are still pasty.
The salts of the British patent compared with the above-described sodium salts do exhibit some advantages. For instance the non-sodium salts described in British Pat. No. 891,631 have the advantage that they do not have a pasty consistency under normal temperature and pressure conditions but are liquid. This cuts down transport costs and is also important for water-free applications of said salts. Most disadvantageously however these known salts have poor color characteristics and are malodorous thereby in reality rendering these salts less suitable for various applications despite contrary statements in text references. In addition, it is difficult to dilute them with water because gel formation takes place.
In addition, the results from other neutralization reactions using triethyanolamine are very discouraging since the thus formed salts are reportedly very pasty in an anhydrous condition even for n values of 2 to 3. Indeed, use of even monoethanolamine and/or ethylethanolamine as the basic component in the neutralization reaction also yields a pasty product.
Surprisingly, it has now been found that in accordance with the present invention that the neutralization of various acid ether sulphates with tri-isopropanolamine yields salts that not only have a suitable odor and color but also are liquid under normal temperature and pressure conditions. Furthermore these novel salts can be dissolved in water without the occurence of gel formation.